JPH03180710A - Flatness measuring instrument for plate - Google Patents

Abstract

PURPOSE:To measure the flatness of the plate for measuring an object to be measured without contacting by providing a polygon mirror, a photodetection part which receives scanning laser light from a steel plate, and a control part which processes signals from them. CONSTITUTION:An equation PA=x=l2/tan(omegat1) holds and is determined by omegat1, where l1 and l2 are the horizontal distances from the reflection position 0 of the polygon mirror 14 to photodetection parts 15 and 16, (h) the height, A and B measurement points on the steel plate right below the photodetection parts 15 and 16, omega the angle of scanning, and P and Q the positions right below the photodetection parts 15 and 16 at the height of the mirror 14. Then when the steel plate is plane, t0=(l/omega)arctan(l1/x) holds and is determined by t1. When, however, the top of the steel plate projects upward, a photodetection part 16 detects the laser light at a position B'. When this time is denoted as t2, delay is larger than at t0 and this delay time corresponds primarily to the flatness of the plate. Therefore, QB'=l1/tan(omegat2) holds and BB' equivalent to the flatness of the plate can be measured when the times t1 - t3 are known.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for electro-optically measuring the temporary flatness of steel plates, wooden plates, etc.

(Prior art and its problems) Conventionally, when measuring the flatness of a plate conveyed on a conveyor, a roller is placed in contact with the plate conveyed on a reference table, and the vertical displacement is actuated. There is a method of measuring flatness using a transformer or the like.

However, in the above-mentioned mechanical measurement method, since the measurement is performed mechanically, there is a problem that the measurement accuracy is poor due to wear of the rollers and the like.

Furthermore, since the thickness or flatness of the plate cannot be measured unless the measuring instrument is brought into contact with the surface of the plate, there is a problem in that it may not be possible depending on the object to be measured.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an apparatus for measuring the flatness of a plate using a laser beam without contacting the object to be measured.

[Means for solving problems]

The flatness measuring device for a plate according to claim 1, which meets the above object, comprises a laser beam transmitter that oscillates a laser beam, and a plate that is an object to be measured by reflecting the laser beam from the laser beam transmitter. A scanning section that scans and irradiates the surface, a light receiving section that receives reflected laser light from the surface of the board and is arranged in parallel at a predetermined interval in the scanning direction, and the flatness of the board is determined from the signal time difference between the parallel light receiving sections. The control unit is configured to include a control unit that calculates the degree.

Further, the plate flatness measuring device according to claim 2 includes:
In the plate flatness measuring device according to claim 1,
The laser beam is high-frequency modulated, and the light receiving section includes a light receiving lens,
It is configured with a light receiving element such as a slit and an APD.

[Function and Examples]

Next, embodiments embodying the present invention will be described with reference to the attached drawings, and the effects of the present invention will also be explained.

Here, FIG. 1 is a side view showing a schematic configuration of a plate flatness measuring device according to an embodiment of the present invention, FIG. 2 is a front view of the same, FIG. 3 is a graph showing signal status, and FIG. FIG. 2 is a diagram for explaining the operation of the cough plate flatness measuring device.

As shown in FIGS. 1 and 2, a plate flatness measuring device 10 according to an embodiment of the present invention includes a laser beam oscillation section 11 that oscillates a modulated laser beam, and a laser beam oscillation section 11 that oscillates a modulated laser beam.
A mirror 12 that reflects the laser beam from 1 and a polygon that is an example of a scanning section and that scans the laser beam in the traveling direction of the steel plate 13 that is the object to be measured.
14, a light receiving section 15.16 that receives the scanned laser beam from the control plate 13, and a control section 17 that processes the signal from the light receiving section 15.16.

The laser beam oscillation section 11 uses a semiconductor laser, and high-frequency modulates the oscillated laser beam using a drive current. Note that it is also possible to provide a separate modulator.

A normal mirror 12 is placed in front of the laser beam oscillation unit 11, and the polygon mirror 14 is irradiated with the laser beam. This polygon mirror 14 is made of a polyhedral mirror, and is driven to rotate at a constant speed by a motor, so as to scan the laser beam in the traveling direction (lengthwise direction) of the steel plate 13.

The above light receiving section 15.16; dry ◆ filter 18.1
9. Condensing lens 20.21, S'') y + 22.2
3 and APD (avalanche photodiode) 24.
25, whose optical axes are parallel and perpendicular to the steel plate 13.

As shown in FIG. 2, five of these plate flatness measuring devices 10 are arranged in parallel in the width direction of the steel plate 13 to form a measuring section 26, and the signal is transmitted to the control section 17. , is processed by a computer located inside.

Note that the plate flatness measuring device 10 disposed in the measuring section 26 can be moved in a horizontal direction according to the width of the plate.

Next, with reference to FIGS. 3 and 4, the horizontal distances of the two light receiving sections 15 and 16 from the reflection position O of the polygon mirror 14 will be described as Q+ , lx, its height is h, and the light receiving part 1
Directly below 5.16! If the so-called fixed points on the board are A and B, and the angular velocity of scanning is ω, then the light receiving section 15.
If the position immediately below is PSQ, ヱΔ−x=j! It becomes 1/1an(ω1+), and (ω1
+). If the steel plate is planar, the time t0 for the light receiving section 16 to detect the laser beam is t
++=(1/ω) arctan(I I/x), which is determined by the above 1+.

However, if the top of the steel plate protrudes upward as shown in FIG.
This delay time (advance time in some cases) corresponds primarily to the flatness of the plate.

Therefore, the result is -ffi, /1an(ωtz), and ffi,
, p2, and ω are known, so if the time t and t2 from the origin signal are known as shown in Fig. 3, then by taking the difference between the above equations, dandan', which corresponds to the flatness of the plate, can be calculated. Can be measured.

Here, if ω is not a constant speed, it is necessary to correct it.

In this embodiment, the light receiving element 27 for detecting the origin signal is provided directly below the polygon mirror 14 as shown in FIG. 1, but since the origin signal serves as a reference,
It can be attached at any position, and furthermore, it is also possible to attach a rotary encoder or the like to the motor that rotationally drives the polygon 14, and use the signal as the origin.

Therefore, the above-mentioned signal processing, that is, arithmetic processing, is carried out by the control section 17 having an internal microcomputer, and the recorder 28
will be displayed on.

In addition, in this embodiment, since the laser light is high-frequency modulated, by detecting only this modulated signal, it is easy to distinguish between disturbance light and signal light, and furthermore, only a specific wavelength can be passed. Interference filter 18.
19, it is possible to block the light emitted from the steel plate.

Furthermore, in this embodiment, since the light receiving parts 15 and 16 are arranged at a location other than the position where the laser beam is regularly reflected, changes in reflectance due to the surface condition and inclination of the steel plate are small, and the flatness of the plate can be stably maintained. can be measured.

In this embodiment, the flatness ratio is indicated by BB', but the present invention can be applied to other methods of defining flatness. Furthermore, it is also possible to use a vibrating mirror that rotates at a certain angle instead of the polygon mirror, and scan the laser beam.

〔Effect of the invention〕

By using the plate flatness measuring device according to claim 1 or 2, the flatness of a plate can be measured in a non-contact manner.

In the plate flatness measuring device according to claim 2, since the laser beam is subjected to high frequency modulation, it can operate stably without causing malfunctions due to disturbance light.

[Brief explanation of drawings]

FIG. 1 is a side view showing a schematic configuration of a flatness measuring device for a plate according to an embodiment of the present invention, FIG. 2 is a front view of the same, FIG. 3 is a graph showing signal status, and FIG. FIG. 3 is a diagram for explaining the operation of the flatness measuring device of FIG. [Explanation of symbols]

Claims (2)

[Claims] (1) A laser beam transmitting section that oscillates a laser beam, a scanning section that reflects the laser beam from the laser beam transmitting section and scans and irradiates it onto the plate surface that is the object to be measured, and a scanning section that reflects the laser beam from the laser beam transmitting section and scans and irradiates the plate surface that is the object to be measured. It is characterized by comprising light receiving sections that receive laser light and are arranged in parallel at predetermined intervals in the scanning direction, and a control section that calculates the flatness of the plate from the signal time difference of the parallel arranged light receiving sections. Board flatness measuring device. (2) The plate flatness measuring device according to claim 1, wherein the laser beam is high-frequency modulated, and the light receiving section has a light receiving element such as a light receiving lens, a slit, and an APD.